This invention relates to a simplified, tandem-axle connecting device, particularly for a commercial vehicle having two tandem axles and more particularly to the rear axle of vehicles for large tonnage road transport.
In general, the two axles of a tandem consist of hollow beams that contain the mechanical elements for transmission of the drive force, called axle tanks. The arms of these tanks connecting their central part to the wheels and through which the axle shafts pass, generally have different zones specially made to:
1. transmit the vertical load,
2. transmit the longitudinal forces passing through the rods for connection with the chassis of the vehicle,
3. transmit the braking forces that pass through the fastening of the brake support.
There are many known systems for connection between the axle tanks and the chassis frame, this latter being generally made up of two parallel and horizontal longitudinal beams; thus, according to known systems, the vertical loads are transmitted through leaf or compressed-air springs, the longitudinal and transverse forces being compensated for by specific fittings, or by the fastening of the leaf springs, or further by the trailing arms.
In any case, the number of parts necessary for taking into account the forces in the above devices is greater than that which results from putting this invention into practice.
Another drawback resulting from axle-chassis connecting systems according to the prior art resides particularly in absorbing the vertical forces at the level of the axle tank.
Actually, the load coming from the fifth wheel of the trailer, and which is directed to the wheels, normally passes through the axle tanks. These latter are handicapped because of the very considerable local reinforcements and the costly machinings that this arrangement imposes on them.
Another negative factor suffered by the axle tanks results from the bending that the absorption of the vertical forces imposes on them and which is proportional to the distance D (or offset) separating the wheel plane from the point of application of said vertical forces. This causes a dimensioning of the tank axle, hence an increase in its bulk, its weight and its price, proportional to the size of offset D.